Risk factors for lymph node metastasis in T1 esophageal squamous cell carcinoma: A systematic review and meta-analysis

Table 1 Baseline characteristics of included studies

Reference	Location	Period	Design	Case	Operation protocol	Lymphadenectomy strategy	LNM/non-LNM	Quality assessment
Aoyama et al[16] (2019)	Japan	2012-2016	SR	50	Esophagectomy	2- or 3-field lymphadenectomy	13/37	6
Chiba et al[24] (2010)	Japan	1992-2008	SR	110	Esophagectomy	Lymphadenectomy	33/77	7
Huh et al[25] (2018)	South Korea	1996-2015	SR	275	Esophagectomy	Lymphadenectomy	40/235	6
Li et al[26] (2013)	China	2006-2011	SR	189	Esophagectomy	Lymphadenectomy	47/95	7
Makuuchi et al[27] (1997)	Japan	1974-1995	SR	133	Esophagectomy	Lymphadenectomy	35/98	6
Min et al[17] (2020)	South Korea	2001-2014	SR	501	Esophagectomy	2-field lymphadenectomy: 462; 3-field lymphadenectomy: 39	140/361	6
Mitobe et al[18] (2013)	Japan	1990-2009	SR	110	Esophagectomy: 106; ER + esophagectomy: 4	Lymphadenectomy	37/73	6
Moon et al[13] (2014)	South Korea	2009-2012	MR	104	Esophagectomy	Lymphadenectomy	15/89	6
Ozawa et al[19] (2016)	Japan	1986-2013	SR	167	Esophagectomy; VATS	2- or 3-field lymphadenectomy	46/121	6
Shen et al[14] (2018)	China	2014-2016	MR	221	Esophagectomy	Lymphadenectomy	53/168	7
Tian et al[15] (2020)	China	2013-2019	MR	243	Esophagectomy	3-field lymphadenectomy	46/197	7
Tomita et al[28] (2008)	Japan	1998-2006	SR	115	Esophagectomy	2- or 3-field lymphadenectomy	52/63	7
Wang et al[29] (2016)	China	2002-2014	SR	228	Esophagectomy	2- or 3-field lymphadenectomy	90/138	6
Wu et al[20] (2018)	China	2002-2010	SR	240	Esophagectomy	2-field lymphadenectomy	39/201	6
Xue et al[21] (2012)	China	1990-2004	SR	271	Esophagectomy	Lymphadenectomy	53/218	6
Yachida et al[22] (2020)	Japan	1986-2010	SR	320	Esophagectomy	3-field lymphadenectomy	93/227	6
Zhou et al[23] (2016)	China	2008-2015	SR	498	Esophagectomy	Lymphadenectomy	87/411	7

ER: Endoscopic resection; LNM: Lymph node metastasis; MR: Multicenter retrospective; SR: Single-center retrospective; VATS: Video-assisted thoracoscopic surgery.

Table 2 Meta-analysis results for the relationship between lymph node metastasis and clinicopathological factors in T1 esophageal squamous cell carcinoma patients

Factors	Studies	Patients	Heterogeneity I2 (P value)	Pooled OR (95%CI)	P value
Age (continuous) (yr)	6	1571	22% (0.27)	-0.81 (-1.75-0.14)	0.10
Sex (male/female)	12	2913	0% (0.78)	1.16 (0.91-1.48)	0.23
Tumor size (> 2/≤ 2) (cm)	6	1482	0% (0.74)	1.93 (1.49-2.50)	< 0.001a
Tumor location (L/U-M)	10	2291	0% (0.57)	1.46 (1.17-1.82)	< 0.001a
T1 substage (T1b/T1a)	15	3558	0% (0.87)	6.28 (4.93-8.00)	< 0.001a
Differentiation (G3/G1-2)	11	1966	0% (0.49)	2.11 (1.64-2.72)	< 0.001a
LVI (present/absent)	11	2226	40% (0.08)	5.86 (4.60-7.48)	< 0.001a
Macroscopic type (nonflat/flat)	6	1213	35% (0.17)	3.17 (2.33-4.31)	< 0.001a
INF (present/absent)	3	591	0% (0.66)	1.82 (0.89-3.73)	0.10

^aP < 0.05. CI: Confidence interval; ESCC: Esophageal squamous cell carcinoma; G1-2: Well differentiated-moderately differentiated; G3: Poorly differentiated; INF: Infiltrative growth pattern; L: Lower; LNM: Lymph node metastasis; LVI: Lymphovascular invasion; OR: Odds ratio; U-M: Upper-middle.